NAME
Array::Heap  treat perl arrays as binary heaps/priority queues
SYNOPSIS
use Array::Heap;
DESCRIPTION
There are a multitude of heap and heaplike modules on CPAN, you might want to search for /Heap/ and /Priority/ to find many. They implement more or less fancy datastructures that might well be what you are looking for.
This module takes a different approach: It exports functions (i.e. no object orientation) that are loosely modeled after the C++ STL's binary heap functions. They all take an array as argument, just like perl's builtin functions push
, pop
etc.
The implementation itself is in C for maximum speed.
FUNCTIONS
All of the following functions are being exported by default.
 make_heap @heap (\@)

Reorders the elements in the array so they form a heap, with the lowest value "on top" of the heap (corresponding to the first array element).
 make_heap_idx @heap (\@)

Just like
make_heap
, but updates the index (see INDEXED OPERATIONS).  make_heap_lex @heap (\@)

Just like
make_heap
, but in string comparison order instead of numerical comparison order.  make_heap_cmp { compare } @heap (&\@)

Just like
make_heap
, but takes a custom comparison function.  push_heap @heap, $element, ... (\@@)

Adds the given element(s) to the heap.
 push_heap_idx @heap, $element, ... (\@@)

Just like
push_heap
, but updates the index (see INDEXED OPERATIONS).  push_heap_lex @heap, $element, ... (\@@)

Just like
push_heap
, but in string comparison order instead of numerical comparison order.  push_heap_cmp { compare } @heap, $element, ... (&\@@)

Just like
push_heap
, but takes a custom comparison function.  pop_heap @heap (\@)

Removes the topmost (lowest) heap element and repairs the heap.
 pop_heap_idx @heap (\@)

Just like
pop_heap
, but updates the index (see INDEXED OPERATIONS).  pop_heap_lex @heap (\@)

Just like
pop_heap
, but in string comparison order instead of numerical comparison order.  pop_heap_cmp { compare } @heap (&\@)

Just like
pop_heap
, but takes a custom comparison function.  splice_heap @heap, $index (\@$)

Similar to
pop_heap
, but removes and returns the element at index$index
.  splice_heap_idx @heap, $index (\@$)

Just like
splice_heap
, but updates the index (see INDEXED OPERATIONS).  splice_heap_lex @heap, $index (\@$)

Just like
splice_heap
, but in string comparison order instead of numerical comparison order.  splice_heap_cmp { compare } @heap, $index (&\@$)

Just like
splice_heap
, but takes a custom comparison function.  adjust_heap @heap, $index (\@$)

Assuming you have only changed the element at index
$index
, repair the heap again. Can be used to remove elements, replace elements, adjust the priority of elements and more.  adjust_heap_idx @heap, $index (\@$)

Just like
adjust_heap
, but updates the index (see INDEXED OPERATIONS).  adjust_heap_lex @heap, $index (\@$)

Just like
adjust_heap
, but in string comparison order instead of numerical comparison order.  adjust_heap_cmp { compare } @heap, $index (&\@$)

Just like
adjust_heap
, but takes a custom comparison function.
COMPARISON FUNCTIONS
All the functions come in two flavours: one that uses the builtin comparison function and one that uses a custom comparison function.
The builtin comparison function can either compare scalar numerical values (string values for *_lex functions), or array refs. If the elements to compare are array refs, the first element of the array is used for comparison, i.e.
1, 4, 6
will be sorted according to their numerical value,
[1 => $obj1], [2 => $obj2], [3 => $obj3]
will sort according to the first element of the arrays, i.e. 1,2,3
.
The custom comparison functions work similar to how sort
works: $a
and $b
are set to the elements to be compared, and the result should be greater than zero then $a is greater than $b, 0
otherwise. This means that you can use the same function as for sorting the array, but you could also use a simpler function that just does $a > $b
.
The first example above corresponds to this comparison "function":
{ $a <=> $b }
And the second example corresponds to this:
{ $a>[0] <=> $b>[0] }
Unlike sort
, the default sort is numerical and it is not possible to use normal subroutines.
INDEXED OPERATIONS
The functions whose names end in _idx
also "update the index". That means that all elements must be array refs, with the first element being the heap value, and the second value being the array index:
[$value, $index, ...]
This allows you to quickly locate an element in the array when all you have is the array reference.
BUGS
Numerical comparison is always done using floatingpoint, which usually has less precision than a 64 bit integer that perl might use for integers internally, resulting in precision loss on the builtin comparison.
This module does not work with tied or magical arrays or array elements, and, in fact, will even crash when you use those.
This module can leak memory (or worse) when your comparison function exits unexpectedly (e.g.
last
) or throws an exception, so do not do that.
SEE ALSO
This module has a rather lowlevel interface. If it seems daunting, you should have a look at Array::Heap::ModifiablePriorityQueue, which is based on this module but provides more and higherlevel operations with an objectoriented API which makes it harder to make mistakes.
A slightly less flexible (only numeric weights), but also slightly faster variant of that module can be found as Array::Heap::PriorityQueue::Numeric on CPAN.
AUTHOR AND CONTACT INFORMATION
Marc Lehmann <schmorp@schmorp.de>
http://software.schmorp.de/pkg/ArrayHeap